ControlMaster CM10, CM15, CM30 and CM50
Universal process controllers and indicators,
1
/
8
,
1
/
4
and
1
/
2
DIN
5 MODBUS Communications
IM/CM/C–EN
17
5.6 Serial Connections
Connections to the MODBUS serial board must be made as shown in Fig. 5.1. Connections to two- or four-wire link
configurations on systems with multiple slaves must be made in parallel as shown in Fig. 5.2. When connecting cable screens,
ensure that ground loops are not introduced.
The maximum serial data transmission line length for both RS422 and RS485 systems is 1200 m (3937 ft.).
The types of cable that can be used are determined by the total line length:
Up to 6 m (19.7 ft.) – standard screened or twisted pair cable.
Up to 300 m (984 ft.) – twin twisted pair with overall foil screen and an integral drain wire.
Up to 1200 m (3937 ft.) – twin twisted pair with separate foil screens and integral drain wires.
